This invention relates generally to liquid level control devices and, in particular, to devices which may be utilized as filler nozzles to control the flow of liquid into a reservoir, storage tank or other container and to control the level of liquid therein. The device of the present invention is particularly useful in an application where automatic shut-off features are desirable.
For instance, in U.S. Pat. No. 3,703,907, a fluid amplifier is disclosed having an inlet and an outlet zone and adapted for use in a liquid reservoir to sense a change of liquid level therein. The amplifier is adapted to be positioned adjacent the desired liquid sensing level in the reservoir and adapted for directing a power stream substantially transversely to the surface of the liquid in the reservoir. Inlet means is constructed and arranged such that a fluid power jet is abruptly altered when the liquid level in the reservoir rises to a sensing level. This abrupt alteration develops a fluid pressure signal which may be used to control various apparatus, such as a pressure responsive fluid valve.
Such fluid amplifiers have been used in various applications. My copending patent application Ser. No. 491,521, filed May 4, 1983 discloses the use of fluid amplifiers in a filling device for use in connection with maintaining proper levels of electrolyte in individual cells of industrial batteries. My copending patent application Ser. No. 404,070, filed Aug. 2, 1982 shows the use of a fluid amplifier wherein the sensing level of liquid in a reservoir is at a remote point from the fluid amplifier itself.
Fluid amplifiers of the character described also have been used in automatic shut-off nozzles as disclosed in U.S. Pat. No. Re. 29,715 wherein a nozzle is shown particularly useful in an application such as self-service gasoline retail outlets.
In the applications of fluid amplifiers described above, the main liquid flow stream also comprises the fluid power stream which develops a pressure signal of a given magnitude. In order to change the signal, all or a major part of the power stream must be altered or diverted to render a signal of a second magnitude. In other words, in order to switch the signal completely off to operate a pressure valve, for instance, which controls the major liquid flow stream, substantially the entire power stream must be deflected at least to some degree. This requires significantly large dimensions for the amplifier to allow the power stream to deflect. The amount and stability of the deflection often is dependent on downstream conditions. In addition, deflection requires a significant amount of control signal flow to enable switching to occur. Although prior fluid amplifiers are very effective in many applications, as described above, particularly due to their excellent pressure recovery, various sizes are required to accommodate a required flow rate.
Furthermore, although prior fluid amplifiers of the character described will function with fluids of various viscosities, the geometry of the fluid amplifier must be altered and optimized for use within relatively narrow viscosity ranges.
There is a need for and it would be desirable to provide a liquid level control device which employs a fluid amplifier and which is substantially independent of the volume of fluid flow, its flow rate as well as the fluid viscosity. This need is particularly prevalent in liquid level control devices incorporating automatic shut-off characteristics. An example of such a need is in nozzles for filling very large tankers where a high volume flow rate is practically mandatory and where high viscosity liquids may be dispensed.